The correct response is:
Heat will flow from the block to the water until both substances have a temperature between 20 degrees Celsius and 300 degrees Celsius.
This is consistent with the principle of heat transfer, where heat moves from a hotter object (the aluminum block at 300°C) to a cooler one (the water at 20°C) until thermal equilibrium is reached, meaning both substances will eventually reach the same temperature. The final temperature will be somewhere between the starting temperatures of the block and the water.